Cross winds combined with certain temperatures are known to lower fan performance and have a detrimental impact on the efficiency of air coolers (AC). This type of apparatus is used in various industries, including petrochemical and process industries, and can include air cooled condensers (ACC) used in power stations. The jetting of air as it passes under the air cooler windwall creates a Venturi effect, often causing the air column in the fans to stall. This problem is more prevalent with the prevailing wind and can be exacerbated by surrounding buildings, trees, tall hedges, etc.
Some shield systems, including those used in connection with ACs, utilise a roller-blind type mechanism to adjust the position of the sheet. Various types of mechanisms for holding the shield at a desired position are known, but these are often mechanically unreliable for sheets of a larger size and/or can be difficult to use.